Apparatus and method for reduction of sonic vibrations in a liquid

ABSTRACT

An apparatus for reduction of sonic vibrations caused when driving a foundation member below the surface of a liquid has a tube structure which is lowered below the surface of the liquid, and which receives the foundation member. A seal is in contact with the tube structure and creates a contained volume around the foundation member, which may be pumped dry so as to minimize the communication of sonic vibrations into the liquid.

FIELD OF INVENTION

The invention relates to an apparatus for reduction of sonic vibrationsin a liquid, when driving down a foundation member below the surface ofthe liquid so that one end is rooted in the bottom of the liquid.

BACKGROUND OF THE INVENTION

A well-known problem for driving down foundation members in an offshoreenvironment, is the sound emission from driving down foundation membersinto the sea bed. Research has shown that fish and sea mammals, within acertain distance from the foundation member being driven in, are atserious health risk due to the sonic vibrations (sound emissions) in thewater and from the sea bed. A number of research papers have stated saidharming effect on fish and sea mammals, from noise and sonic vibrationsdue to foundation members, such as monopiles being driven into the seabed, e.g.: “Technical Guidance for Assessment and Mitigation of theHydroacoustic Effects of Pile Driving on Fish”, February 2009, Preparedfor: California Department of Transportation, Contact: Jim Andrews.Prepared by: ICF Jones & Stokes, 630 K Street, Suite 400, Sacramento,Calif. 95818, Contacts: Rick Oestman, Dave Buehler And: Illingworth andRodkin, Inc, 505 Petaluma Blvd. South, Petaluma, Calif. 94952, Contacts:James Reyff, Rich Rodkin.

JP60159218A describes an onshore sound insulator using a flexible gasfilled sleeve in shape of bellows surrounding the mono pile while beingdriven by a pile hammer. The bellow, containing gas and water, functionsas a spring and damper solution in an onshore environment, but willtransfer noise emission if used in an offshore environment, surroundedby water.

DE10302219 describes an offshore solution in which the pile or post isnoise insulated from the surrounding water by a large number of gasfilled compartments or cells.

WO2007096132 describes an offshore solution in which the pile or post isnoise insulated by a noise reduction sleeve in a cofferdam structure, asthe pile is positioned in a water-free environment, while being driveninto the sea bed.

SUMMARY OF THE INVENTION

Considering the prior art described above, it is an object of thepresent invention to provide an apparatus and a method for a fast and acheap way of driving down foundation members in the bottom of a liquid,such as an ocean, while ensuring minimal sonic vibration in order tominimise the environmental impact.

The object can be achieved by means of an apparatus for reduction ofsonic vibrations in a liquid, when driving down a foundation memberbelow the surface of the liquid, so that one end is rooted in the bottomof the liquid comprising a tube structure adapted for lowering a sectionof the tube structure below the surface of the liquid and suitable forlongitudinally positioning the foundation member within the tubestructure; sealing means in contact with the tube structure and adaptedto create a contained volume by contact between the section of the tubestructure below the surface and the foundation member, when thefoundation member is positioned longitudinally within the tube structurefor driving down the foundation member; pumping means adapted to removeliquid from the contained volume when the foundation member ispositioned longitudinally within the tube structure and the containedvolume has been created.

Thus, it is possible to reduce the sonic vibrations when driving downfoundation members in the bottom of a liquid, such as an ocean or alake. Further, the invention is suitable for use off shore as it isrelatively simple and cheap.

The use of sealing means reduces the amount of liquid that re-enter thecontained volume after liquid has been removed. This is advantageousbecause it decreases energy and/or fuel consumption of the pumps.

The tube structure is a hollow longitudinal structure, preferably acylinder; however, other shapes can also be used as long as thefoundation member can be positioned longitudinally within the tubestructure. The cross-sectional shape of the tube structure can, forexample, be square, rectangular or hexagonal. In an embodiment, the tubestructure has the same cross-sectional shape as the foundation member.The tube structure can, in an embodiment, be interpreted as a cofferdam.The tube structure can be lowered to and/or be kept at a desired heightabove the bottom of the liquid.

Foundation members, preferably monopiles, can be used to create afoundation for offshore structures, such as wind turbines. They can beembedded in the ground by driving them into the bottom of the liquid;the depth of the foundation members in the ground depends on theintended use of the foundation members and the geology of the site. Inan embodiment, the foundation member comprises a plurality of separatesections, joined when driven down.

Contained volume can be understood as the volume between the foundationmember and the tube structure in the section where they overlap and aredelimited in the bottom by the sealing means. In an embodiment, thecontained volume is also delimited at the top and filled with a gas, inorder to reduce the sonic vibrations to a desired level.

Preferably, the contained volume is open to the atmosphere. This can beobtained by having no additional sealing means between the foundationmembers and the tube structure. They pressure inside the containedvolume will then be approx. 1 atm and equal to the surrounding air. Thesonic vibrations generated when the foundation member is being drivendown, e.g. by a hammer, are then transferred to the air with in thecontained volume. Substantially all these sonic vibrations are thenequalised through the opening to the atmosphere and consequently nottransferred to the tube structure and onwards to the liquid. In otherwords, the contained volume directs a substantially amount of the sonicvibrations generated when driving down the foundation member up and outinto the atmosphere, hereby reducing the sonic vibrations in the liquid.

The sealing means, for example a gasket or another mechanical packing,can ensure that only small amounts of liquid enter the contained volume.By small amounts, it is to be understood, that the flow of liquid intothe contained volume should not exceed the pumping capacity of thepumping means. It is preferred to make the sealing means as tight aspossible, as it will save energy used by the pumping means. The pumpingmeans can be a liquid pump, suitable for pumping the relevant liquid. Itis preferred to place the pumping means below the surface of the liquidand/or near the sealing means with an inlet at the bottom of thecontained volume.

The tube structure is preferably lowered into the liquid, before thefoundation member is positioned within the tube structure, preferably bylowering it into the foundation member. Alternatively, the foundationmember can be positioned within the tube structure before lowering asection of it below the surface of a liquid.

In an embodiment, the apparatus further comprises a support structurecomprising a plurality of pivotable legs connected to the tubestructure, wherein the plurality of legs are adapted to support the tubestructure by positioning the plurality of legs on the bottom of theliquid. The support structure can then be used to position itself withany desired inclination. In addition, the support structure can bedesigned to support itself to make it possible to leave the supportstructure on the bottom of the liquid, either with the foundation memberinserted or for later insertion, in order to drive down the foundationmembers at a later time. Preferably, the support structure has threelegs evenly distributed around it. The angle between the legs and thesupport structure can be changed in order to ensure the desiredinclination.

In an embodiment, the apparatus further comprises a support structureadapted to hold the tube structure in a substantially vertical position.It is preferred to have a vertical position of the support structure,regardless of the inclination at the bottom of the liquid, as a verticalposition provides the best conditions for structures using thefoundation members as part of their foundation.

Preferably, the sealing means are fixed to the tube structure. The tubestructure can be reused on a plurality of foundation members and thesealing means are also reusable. Hence, it is desirable that they arejoined. This will result in a more simple and easy handling of thepresent invention.

Advantageously, the sealing means comprises an expandable section,adapted to be expanded when the foundation member is positionedlongitudinally within the tube structure, hereby securing a tight seal.This is a way of ensuring that the seal is as tight as possible and atthe same time makes lowering the foundation member more simple, as theexpandable section can be unexpanded when lowering the foundation memberand then expanded afterwards. The lowering does, consequently, not haveto deal with a tight sealing member until driving down of the foundationmember is initiated. This also protects the sealing means against wear.

In an embodiment, the tube structure comprises telescopic sectionsadapted to elongate or contract the tube structure. This will ease thehandling of the tube structure and is especially desirable when the tubestructure is of considerable length, such as over 10 meters. Inaddition, telescopic sections can ensure that the section of the tubestructure that is above the surface of the liquid has the same heightfor a plurality of tube structures even when they are positioned atdifferent depths.

The invention further regards a system comprising a plurality ofapparatuses as described herein, wherein the plurality of apparatusesare joined by at least one distance piece to ensure a predeterminedposition of foundation members positioned in the tube structures inrelation to each other. The distance piece or pieces can be used to jointube structures and thereby make a predefined pattern possible. If, forexample, pluralities of structures are in need of a foundation with morethan one foundation member, it can be an advantage to have a system oftube structures and distance pieces to form a fixed template for thefoundation members. In an example, distance pieces form a square withtube structures at the corners; it is then possible to position fourfoundation members precisely in the correct position in relation to eachother. The system can then be elevated over the foundation members andused for driving down four new foundation members.

Another aspect of the present invention regards a method for reducingsonic vibrations in a liquid when driving down a foundation member belowthe surface of the liquid, so that one end is rooted in the bottom ofthe liquid, comprising the steps of: Lowering a section of a tubestructure below the surface of the liquid, inserting a foundation memberinto the tube structure, creating a contained volume between thefoundation member and the tube structure with sealing means in contactwith the foundation member and the tube structure, removing liquid fromthe contained volume, sequentially driving down the foundation memberinto the bottom of the liquid with reduced sonic vibrations.

When executing this method, the sonic vibrations connected with drivingdown foundation members in a liquid, is greatly reduced to the benefitof the fish and sea mammals in the vicinity.

In an embodiment, the method further comprises the step of adjusting theinclination of the tube structure. This is advantageous because itensures that the foundation can be positioned and inclined to supportany structure desired. Preferably, the adjusting of the inclination ofthe tube structure is performed by use of a support structure,preferably comprising a plurality of legs with one end supporting thetube structure and the other resting at the bottom of the liquid. Thebottom of the liquid can have different inclinations and normally it isdesired that the inclination of the foundation member is vertical. Asupport structure as mentioned can be used to ensure that.

Advantageously, after the foundation member has been driven down intothe bottom, the following step is performed: raising the tube structureabove the foundation member and thereby removing the tube structure fromthe foundation member. The tube member can then be used when drivingdown another foundation member.

Preferably, the tube structure is lowered to the bottom of the liquid.It can then be supported by the bottom and is then easier to control. Inaddition, it can be left standing on the bottom for later use.

In an embodiment, the tube structure comprises telescopic members forelongation and contraction of the tube structure. This is advantageouswhen the tube structure is of considerable length. Transportation to thesite where it will be lowered is then made easier.

In an embodiment, lowering of a section of a tube structure below thesurface of the liquid is performed from a vessel adapted to float on theliquid. This is desirable as it is a simple way to transport theapparatus to where the foundation member is to be driven down.Preferably, the vessel comprises at least one pole which is lowered tothe bottom of the liquid in order to support the vessel. Preferably thevessel is raised above the surface of the liquid while standing on atleast one pole. The vessel can be a jack-up rig, which gives very stableconditions for driving down foundation members offshore.

In an embodiment, a plurality of tube structures, joined together bydistance pieces, are used when driving down foundation members in apredefined pattern. This enables a predefined pattern of the foundationmembers.

It is to be understood that the method can be adapted for use of thementioned apparatus and vice versa.

DESCRIPTION OF THE DRAWINGS

The invention will in the following be described in greater detail withreference to the accompanying drawings:

FIG. 1A, 1B a schematic view of an embodiment of the invention with atube structure ready to be lowered.

FIG. 2A, 2B a schematic view of an embodiment of the invention with atube structure resting on a vessel.

FIG. 3A, 3B a schematic view of an embodiment of the invention with atube structure being lowered.

FIG. 4A, 4B a schematic view of an embodiment of the invention with atube structure being stabilised by the support structure.

FIG. 5A, 5B a schematic view of an embodiment of the invention with afree standing tube structure stabilised by a support structure.

FIG. 6 a schematic view of an embodiment of the invention with a tubestructure being stabilised by a support structure and driving down afoundation member by a hammer.

FIG. 7 a schematic view of an embodiment of the invention with a tubestructure supported by a support structure and a foundation memberfounded in the bottom.

FIG. 8A, 8B a schematic view of an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention addresses the problem of, speedily, driving downone or more foundation members, preferable monopiles, into the bottom ofa liquid, to create a foundation for structures in an offshoreenvironment, such as Wind turbines. It provides an apparatus and methodof foundation in an environmentally friendly way, for example, to theinstallment of multiple wind generators in offshore wind farms. In anexample, it can be done by a positionable, self-supporting, temporarycofferdam, by transferring, positioning, adjusting, the temporarycofferdam from a vessel to the desired position on the bottom of theocean, enabling early placing and adjustment of cofferdam and laterdriving in the foundation member.

An aspect of the present invention is a method for environmentallysafety as well as speedy foundation member installation for use inoceans and lakes. Preferably, including a method for transporting atemporary cofferdam structure to a construction site, transfer of thesecofferdam structures to the bottom of the flooded area, whereinstallation position and angle is adjusted by means of adjustable legsor the like, to enable a self-supporting cofferdam in the ocean or lake.A contained volume between the cofferdam structure and the foundationmember is then created. Pumps then remove water from the containedvolume resulting in air entering through the opening in the top. Thisreduces transportation of hydro acoustic effects from driving down thefoundation member into the bottom of the ocean or lake, which ensuresminimal amount of vibrations to the surroundings. The apparatusaccording to the present invention is preferably transported on anddeployed from a vessel that is able to move or be moved, for example afloating transportation vessel, such as a boat or a jack-up rig.

FIG. 8A and 8B shows an embodiment of the present invention, a tubestructure 3 has been partly lowered into a liquid. The tube structure 3can be held in place by a jack-up rig, boat or support means with legsresting on the bottom of the liquid 9. The tube structure 3 rests on thebottom 9. Resting the tube structure 3 on the bottom 9 can help instabilising the tube structure 3. Within the tube structure 3, afoundation member 10 has been lowered. Both the tube structure 3 and thefoundation member 10 extend over the surface of the liquid 14. Thesealing means 7 are fixed to the tube member 3 and is in sealing contactwith the foundation member 10. The pump 15 can then empty the liquidinitially present in the contained volume 12. The pump 15 has an inletconnected with the contained volume 12 and outlet in the liquid. Thecontained volume 12 can then be kept substantially free from liquid,while the foundation member 10 is driven down into the bottom 9, forexample by a hammer. The skilled person will know, that it is verydifficult the keep sealing means 7 entirely tight as the foundationmember 10 is moved in relation to the sealing means when driven into theground 9. It is therefore necessary to keep the pumps running throughoutthe operation of driving down the foundation members 10, in order toensure a substantially liquid free contained volume 12. The reduction ofsonic vibrations in the liquid is reduced due to the liquid free sectionof the contained volume 12. FIG. 8A shows a tube structure 3 in onepiece whereas 8B shows a telescopic tube structure 3.

FIG. 1 disclose a simplified sketch of the present invention in anembodiment comprising an offshore vessel 1, jack-up legs 2, tubestructure 3 (also known as cofferdam structure) with adjustable legs 4,tube structure lifting system 5, tube structures in storage area 6 andsealing means 7. The jack-up vessel 1 provides a stable platform fortransport and placing of the tube structures 3.

FIG. 2 shows a simplified sketch of an embodiment of the presentinvention with a tube structure 3 transferred from store to cofferdamstructure lifting system 5 by the transfer system 8.

FIG. 3 shows a simplified sketch of the invention at hand in anembodiment showing a tube structure 3 being lifted to the bottom 9 ofthe liquid by the tube structure lifting system 5.

FIG. 4 shows a simplified sketch of the invention at hand in anembodiment showing a tube structure 3 being angular adjusted by theadjustable legs 4 on the tube structure 3.

FIG. 5 shows a simplified sketch of the invention at hand in anembodiment showing a tube structure 3 being positioned on the sea bed 9for later driving down of the foundation member 10.

FIG. 6 shows a simplified cut through sketch of the invention at hand inan embodiment showing a foundation member 10 being driven into the seabed 9 by a pile driving hammer 11, while the contained area 12, betweenthe tube structure 3 and pile 10 is kept dry by means of a pump, thiswill reduce the sonic vibrations generated when the foundation member isdriven down in the bottom 9. In addition, an auxiliary noise reductionsystem is blowing out gas in to the surrounding sea water, surroundingsaid tube structure 3 with a gas bubble curtain 13, which reduces thesonic vibrations from the driving down of the foundation member 10 evenfurther. The auxiliary noise reduction system can use a pump forgenerating the bubble curtain, and preferably the pump is the same pump15 as used for emptying the contained volume 12 from liquid.

FIG. 7 shows a simplified sketch of the invention at hand in anembodiment showing a foundation member 10 in final position with thetube structure 3 still enclosing it.

Afterwards the tube structure 3 is, preferably raised and removed fromthe foundation member 10.

An embodiment of the invention is described in the following:

An embodiment of the invention relates to a method of establishing atemporary cofferdam structure in a flooded environment, to allow drivingin the foundation for a structure on the bottom of a flooded environmentin an environmentally friendly way, including the steps of transportinga cofferdam structure to the right position, lowering said cofferdamstructure to proper contact with said bottom of said floodedenvironment, positioning said cofferdam structure in proper angle by useof said cofferdam structures self-contained adjustable structure,inserting and driving down said foundation member, after which, saidcofferdam structure will be raised to ensure that it has no metalcontact with said newly driven in foundation member. The cofferdamstructure and the foundation member, together, when the said foundationmember is installed in the cofferdam structure, enables a containedvolume, enabling said foundation members outer perimeter to be kept ofdirect contact with the fluid of flooded environment. Said containedvolume is secured by an installed seal between said cofferdam structureand said foundation member.

Preferably, said contained volume is made by emerging the cofferdamstructure partly into sealing contact of said bottom of said floodedenvironment. Using the material of said bottom as seal.

Preferably, said cofferdam structure is made out of 2 or more telescopicparts relatively elongateable to each other, to allow for differentwater levels and easier lifting and or transportation of a cofferdamstructure.

Preferably, said contained area is kept secured by letting said seal beof an expandable type, enabling a tight seal, even at depts.

Preferably, said contained area is kept secured by letting said seal ofan expandable type be expanded by a gas, fluid or a mix of the two, toenable a chosen expandability or contraction.

Preferably, said foundation member is of a hollow type, enabling anadditional contained area while said foundation member is in a sealingcontact with the bottom of the flooded environment, this contained areaallows adjusting of vibrational characteristics of said foundationmember.

Preferably, one or more contained volume is filled, partly or fully,with gas to allow adjusting of vibrational characteristics of saidfoundation member.

Preferably, said one or more contained volume is emptied, partly orfully, to allow adjusting of vibrational characteristics of saidfoundation member.

Preferably, said one or more contained volume is filled, partly orfully, with a mixture of gas and fluid to allow adjusting of vibrationalcharacteristics of said foundation member.

Preferably, said one or more contained volumes is used as insulation toallow adjusting of vibrational characteristics of said foundationmember.

Preferably, said one or more contained volume is emptied, partly orfully, with a pump to allow adjusting of vibrational characteristics ofsaid foundation member.

Preferably, said one or more contained volumes are filled, partly orfully, with a mixture of gas and fluid with a pump to allow adjusting ofvibrational characteristics of said foundation member.

Preferably, the driver, driving down said foundation members into saidbottom of said flooded environment is a Hammer or a Hammer likemechanism.

Preferably, the driver, driving down said foundation members into saidbottom of said flooded environment is a vibrator.

Preferably, the method or system is installed on a vessel fortransportation in a flooded environment; this might be any kind ofrelevant vessel.

Preferably, a gas bubble curtain being blown out, around the extendableguide, at the lower part of the extendable guide, while driving in saidfoundation member to reduce noise mitigation from said extendable guideand said foundation member, to the flooded environment.

The term “flooded environment” can be a saltwater-based area or afreshwater-based area or mixture hereof. The saltwater based area can bethe ocean or a lake and the freshwater based area can be a lake, river,pond, or an artificially flooded area created by humans.

Preferably, said transportation unit for transportation in a floodedenvironment is a floating transportation unit, like a ship, a boat, apram or other floating transportation units.

Preferably, said transportation unit for transportation in a floodedenvironment is a wheel based, belt driven or other rolling or drivingtransportation unit, like a truck, a crane or other wheel based, beltdriven or other rolling or driving transportation units.

Preferably, said transportation unit for transportation in a floodedenvironment is a flying or hovering transportation unit, like a plane, ahovercraft, a helicopter or other flying or hovering transportationunits.

Preferably, said transportation unit for transportation in a floodedenvironment is a jack-up type vessel.

Preferably, said foundation member is a monopile.

Preferably, said foundation member is a construction of steel, concrete,plastic, composites, ceramics, other rigid or semi-rigid material or anymixture hereof.

Preferably, said self-contained adjustable structure contains one ormore legs for interacting indirectly or directly with said bottom toalter or stabilize the angle of said cofferdam structure relatively withsaid bottom.

Preferably, said self-contained adjustable structure contains one ormore pivot able members interacting with said bottom to alter orstabilize the angle of said cofferdam structure relatively said bottom.

Preferably, said self-contained adjustable structure contains one ormore elongation able members interacting with said bottom to alter orstabilize the angle and/or alter the horizontal position of saidcofferdam structure relatively said bottom.

Preferably, said driving of foundation members into a bottom of aflooded environment is made by means of rotation of the foundationmember relative to said cofferdam structure.

Preferably, said driving of foundation members into a bottom of aflooded environment is made by means of rotation of a fluid or stiffmedia inside the foundation member relative to said bottom of saidflooded environment.

1. An apparatus for reduction of sonic vibrations in a liquid whendriving down a foundation member below the surface of the liquid so thatone end is rooted in the bottom of the liquid, said apparatuscomprising, a tube structure adapted for lowering a section of the tubestructure below the surface of the liquid, said tube structure beingoperable for longitudinally positioning the foundation member within thetube structure, sealing means in contact with the tube structure, saidsealing means being operable to create a contained volume by contactbetween the section of the tube structure below the surface and thefoundation member when the foundation member is positionedlongitudinally within the tube structure for driving down the foundationmember, pumping means being operable to remove liquid from the containedvolume when the foundation member is positioned longitudinally withinthe tube structure and the contained volume has been created.
 2. Theapparatus according to claim 1, wherein the apparatus further comprisesa support structure comprising a plurality of pivotable legs connectedto the tube structure, wherein the plurality of legs are operable tosupport the tube structure by positioning the plurality of legs on thebottom of the liquid.
 3. The apparatus according to any of the precedingclaim 1, wherein the apparatus further comprises a support structureoperable to hold the tube structure in a substantially verticalposition.
 4. The apparatus according to claim 1, wherein the sealingmeans are fixed to the tube structure.
 5. The apparatus according toclaim 1, wherein the sealing means comprises an expandable sectionoperable to be expanded when the foundation member is positionedlongitudinally within the tube structure hereby securing a tight seal.6. The apparatus according to claim 1, wherein the tube structurecomprises telescopic sections operable to elongate or contract the tubestructure.
 7. The apparatus according to claim 1, wherein the containedvolume is open to the atmosphere.
 8. A system comprising a plurality ofapparatuses according to claim 1, wherein the plurality of apparatusesare joined by at least one distance piece so as to ensure apredetermined position of said foundation members positioned in the tubestructures in relation to each other.
 9. A method for reducing sonicvibrations in a liquid when driving down a foundation member below thesurface of the liquid so that one end is rooted in the bottom of theliquid, said method comprising the steps of lowering a section of a tubestructure below the surface of the liquid, inserting a foundation memberinto the tube structure, creating a contained volume between thefoundation member and the tube structure with sealing means in sealingcontact with the foundation member and the tube structure, removingliquid from the contained volume, sequentially driving down thefoundation member into the bottom of the liquid whereby sonic vibrationsare reduced.
 10. The method according to claim 9, further comprising thestep of adjusting the inclination of the tube structure.
 11. The methodaccording to claim 10, wherein the step of adjusting the inclination ofthe tube structure is performed by use of a support structure comprisinga plurality of legs with one end supporting the tube structure and theother resting on the bottom of the liquid.
 12. The method according toclaim 9, wherein after the foundation member has been driven down in thebottom, the following step is performed: raising the tube structureabove the foundation member and thereby removing the tube structure fromthe foundation member.
 13. The method according to claim 9, wherein thetube structure is lowered to the bottom of the liquid.
 14. The methodaccording to claim 9, wherein the tube structure comprises telescopicmembers for elongation and contraction of the tube structure.
 15. Themethod according to claim 9, wherein lowering a section of a tubestructure below the surface of the liquid is performed from a vesseladapted to float on the liquid.
 16. The method according to claim 15,wherein the vessel comprises at least one pole which are lowered to thebottom of the liquid in order to support the vessel, and wherein thevessel is raised above the surface of the liquid while standing on theat least one pole.
 17. The method according to claim 9, wherein aplurality of tube structures, joined together by distance pieces, areused when driving down foundation member in a predefined pattern.